Fluid pressure brake



May Z6, 1936.

J. B HULL FLUID PRESSURRBRAKE Filed May 9, 1934 .mmh

Patented May 26, 1936 UNIT STATES PTET QFFEQE FLUID PRESSURE BRAKEApplication May 9, 1934, Serial No. 724,666

17 Claims.

This invention relates to fluid pressure brakes and particularly tobrake controlling valve devices therefor.

Under certain conditions it is desirable to effect service applicationsof the brakes with greater rapidity than present brake controllingdevices permit, in order to' obviate the necessity for an emergencyapplication of the brakes with its` consequent penalty of greaterrelease time and greater amount of recharge fluid, as well as of shockand discomfort to passengers.

Present fluid pressure brake controlling devices are so designed thatany substantial increase in the rate of brake pipe pressure reductionover lthe usual service rate of reduction effects an emergencyapplication of the brakes. It is thus impossible to increase therapidity of a service application, when employing present standard brakecontrolling devices, by increasing the rate of brake pipe pressurereduction any substantial degree beyond the usual service rate ofreduction.

It is the principal object of my invention, therefore to enable serviceapplications of the brakes to be effected with greater rapidity thanheretofore by providing a iluid pressure brake controlling device whichis responsive to a brake ,pipe pressure'reduction at any rate in excessof the usual service rate of reduction to effect a service applicationof the brakes without the possibility of an emergency application of thebrakes being effected.

Another object of my invention is to provide means for simply andinexpensively adapting present standard brake controlling devices tooperate as stated in the principal object explained above.

A further object of my `,invention is to p-rovide a fluid pressure brakecontrolling device of the character as above described which isunresponsive to any rate of brake pipe pressure reduction to effect anemergency application of the brakes unless a predetermined reduction inbrake pipe pressure has been effected.

A still further object of my invention is to provide a duid pressurebrake apparatus, including a brake controlling device of the characteras above described, wherein the reduction in brake pipe pressure for aservice application is automatically limited to a predetermined maximumamount and an undesired emergency application of the brakes therebyprevented.

Other objects and advantages of my invention will be made apparent inthe subsequent description of one illustrative embodiment thereof, whenread in connectionwith the accompanying drawing, wherein Fig. 1 is aview, partly in section, showing the essential features of oneembodiment of my invention with the equipment in release position.

Fig. 2 is a diagrammatic view, showing the various connectionsestablished by `the brake valve of Fig. v1, when in the several brakeoperating positions.

Referring to Fig. il, theA embodiment shown may comprise anyl brakecontrolling valve mechanism, such as the triple valve mechanism Il,which is connected to a brake pipe l2, a brake valve I3, a feed valveI4, abrake cylinder I'5,'an auxiliary reservoir I6, asupplementaryreservoir l1, ra main :reservoir 18, Van equalizingreservoir I9, and a reduction limiting reservoir 2D.

The triple valve mechanism .H Vmay comprise four casing sections, namelya slide valve section 23, a high pressure valve'se'ction2.4,.apipeconnecting bracket section '125, and an emergency blockingvalve section'26.

Casing section .23 contains a `chamber 21 :connected to brake pipe I2and having `a piston 2-8 operable therein, and a chamber 29 connected tothe auxiliary reservoir I6 and Vcontaining afmain slide valve 30 and anauxiliary slide valve3l, both adapted to be operated by the'piston 28through a stem 32 in theusual manner.

The casing section 24 containsia chamber 35 continuously connectedtoslidevalve vchamber Y29 through a passage 36 andbranch passage .31 andhaving va piston 38 operable Ltherein, a chamber 39 at the opposite sideof the piston38zalso-being provided which is'also connectedtoV the slidevalve chamber 29 through a passage and port All. The port 40 is underthe control of :main slide 'valve 30 which operates to vent chamber 39when moved to emergency position in the manner hereinafter described.

The piston 38 is provided l.with astem `12"by means of which'it isadapted `to operate awvalve '43 contained in a chamber 7AllVWhich'iscontinuously connected to the supplementary reservoir I1through a passage and pipe 45. Valve43 Vis adapted to be biasedintolseating relation on `an annular rib seat 46 .when thepressuresinchambers 35 and 39 ron vopposite sides vof piston 38 areequal, by aspring 'Gl disposed inchamber 44 between the valve 43 and asuitablescrew plug 48, which plug closes the 4'chamber 44.and;isadjustable to vary the tension of spring 4l.

Intermediate of the kchambers .3,9 and 44 is a chamber A9, which iscontinuously connected :to the slide valve chamber '.29 through passageA3.6

and which is adapted to be connected to chamber 44, when valve 43 isunseated, through a passage 5| leading from chamber 48 to the innerseated area of valve 43. Thus when valve 43 is unseated, thesupplementary reservoir I1 is connected to slide valve chamber 29.

The casing section 25 contains various passages for establishing thenecessary connections to the brake pipe I 2, to the brake cylinder I5,to the auxiliary reservoir I6 and to the supplementary reservoir I1, ashereinafter described.

The casing section 26, embodying the principal feature of my invention,may contain a chamber 54 open to the piston chamber 21 through one ormore ports 55 and connected to the brake pipe I2 through passage andpipe 56, and a chamber 51 open to chamber 54 and containing a stopmember 58, which is normally biased against the end wall of casingsection 26 by a spring 59, and which is provided with an extension 60that passes through a, closely tted opening in the end wall of thecasing section 26 into piston chamber 21. The extension 60 of stopmember 58 is disposed in axial alignment with the piston 28 and isadapted to be engaged thereby upon a brake application as hereinafterdescribed.

Casing section 26 also contains a chamber 65 connected to chamber 51through a passage 65 and having therein a piston valve 61 provided witha stem 68 which is suitably supported in axial alignment with extension60 of the stop member 58 and which is of such length that the endthereof is spaced from the inner surface of the stop member 58 a shortdistance.

The piston valve 81 is provided, on the side opposite chamber 65 with asealing gasket 69,

adapted to engage an annular seat rib 10 at the end of a hollow tubularportion 1I of the casing 26, which tubular portion 1| is supported by anannular imperforate rib or wall 12 separating chamber 51 on one sidethereof and another chamber 13 open to atmosphere through a chokeVpassage 14. The interior of the tubular portion 1| constitutes a passage15 which is open to cham- 'ber 51 a-t one end through ports 16.

It will thus be seen that piston valve 61 is subject to the differentialof the brake pipe pressure in chamber 65 acting on entire outer face ofthe piston, and the brake pipe pressure acting o'n the inner seated areaof the piston valve 61, the outer seated area of piston valve 61 beingsubject only to atmospheric pressure. Piston valve 61 is thus maintainedin sealing relation on seat rib 10 by the-excess pressure in chamber 65,aided to some extent by a spring 11 disposed in chamber 65 between thepiston valve and a screw plug 18 closing the end of chamber 65. Spring11 is primarily designed to effect return movement of piston Valve 61into sealing engagement with seat rib 10, as will be hereinafter pointedout.

The spring 59 and stop member 58 may be omitted, if desired, and thestem 68 extended in length to protrude through the opening in the casingwall into piston chamber the same distance as extension 60 of the stopmember. Spring 59 and stop member 58, when employed, act however tosoften the initial blow of the piston upon a brake application. The endof stem 68 is spaced a short distance from the back surface of stopmember 58 to insure proper and full seating of piston valve 61 on ribseat 10.

The brake valve I3 is of usual construction, being illustrated forsimplicity as comprising only those features essential to the operationof the system disclosed. Briefly, however, it comprises the usualplurality of main body casing sections 80 suitably secured in sealedrelation and a cap section 8| enclosing a chamber 82 above the uppermostsection 80, in which chamber a rotary valve 83 is disposed, the valve 83being operated manually into the usual brake operating positions, asillustrated in Fig. 2, by a lever or handle 84 through a stem 85projecting through a sealed opening in the cap section 8| and suitablyinterlocked with the rotary valve 83. The stem 85 has a recess in theend thereof in which a spring 86 is disposed to urge a collar or flangeon the valve stem 85 in sealing contact against the cap section 8| ofthe casing.

Contained within the brake valve sections 80 is an equalizing piston 81for operating a vent valve 88, the piston 81 having at one side anequalizing chamber 89 which is continuously connected to the equalizingreservoir I9 through a passage and pipe 90, and at the other side achamber 9| which is 'continuously open to the brake pipe I 2 throughpassages 92 and 93. When the iiuid pressure in chamber 9| exceeds thatin equalizing chamber 89, the piston 81 is raised and unseats vent valve88 so that the brake pipe and chamber 9| are vented -to atmospherethrough an exhaust passage and port 94 which may be of an area so as toeffect any desired rate of brake pipe pressure reduction in excess ofthe usual service rate.

An exhaust port and passage 95 opens at the rotary valve seat and thereduction limiting reservoir 20 is connected thereto in the releaseposition of the brake valve, by a pipe and passage 95 and a cavity 91 inthe rotary valve, as shown in Fig. l.

With the brake valve 83 in service application position, as shown inFig. 2, the reduction limiting reservoir 20 is connected to theequalizing chamber 89 and equalizing reservoir IS through pipe andpassage 96, a cavity 9B in the rotary valve 83 which cavity contains arestricted opening 99 (see Fig. 2), and a passage |0I. The restrictedopening 99 controls the rate of flow of fluid from the equalizingreservoir I 9 to the reduction reservoir 20, and thus controls theoperation of the equalizing piston 81 to vary the rate of opening ventvalve 88.

'Ihe brake pipe I2 is charged with fluid under pressure from mainreservoir I8, through feed valve I4, pipe and passage I 02, chamber 82of brake valve I3, port |03 in the rotary valve 83 and passage and pipe93. The equalizing chamber 89 and the equalizing reservoir 20 arecharged with fluid at brake pipe pressure through cavity |04 openinginto port |03 of the rotary valve 83, and passage |0I, while chamber 9|beneath the equalizing piston 81 is also charged with fluid at brakepipe pressure through passage 92 connected to pipe and passage 93. Thepressures on opposite sides of equalizing piston 81 being thus balanced,the piston 89 'maintains vent valve 88 seated or closed.

Fluid under pressure iiows from the brake pipe I2 to piston chamber 21through pipe and passage 55, chamber 54 and ports 55, and continues onpast the piston 28 through the usual feed groove |01 into slide valvechamber 29. From the slide valve chamber 29, fluid flows to theauxiliary reservoir I6 through passage ,and pipe |08, and to thesupplementary reservoir I1 through a port |89 in the main slide valve30, port and passage IIO in the seat of the slide valve, and passage andpipe 45, thus charging both reservoirs with fluid at brake pipepressure. Valve chamber 44, `being connected to the supplementaryVreservoir '|:I, isthusalso charged with Auid under pressure, as arechambers 35 land -39 'which l'are connected tothe 'slidevalve-'ohamberas described above.

The -pressures on 'opposite sides of piston 38 `being equal, Aspring F41iis eiective to vvbias valve #3 into seated or c'losed position.

Fluid under pressure from chamber i515 also flows into chamber :51 andfrom thence through passage into chamber 65 lso'that piston Avalve 61 iscaused to-seat firmly on the rib .seat 18, the 'fluid Vunder pressure'from chamber '54 supplied through ports 'IBandpassage :15 andleffectiveon the inner seated `area 'of 'the piston valve being -overbalaneed by4the pressure eiective 'on the outer area thereof in ychamber 65.

If it'be desired to elect a 'service lapplication of the brakes, thebrake valve 'I3 is moved to the usual service application positionwherein the -equalizing reservoir If9 is connected to the reductionlimiting reservoir'l, as 'above described kandas `shown in Fig. -2.Fluid `under pressure is thus supplied to the reduction limitingreservoir `at a rate dependent upon the size ofthe restricted opening9'9`in 'cavity 98 of the'rotary valve 83. As

the pressure in equalizing chamber 89 reduces, equalizing piston '81 Yisforced upwardly by the brake pipe pressure effective in chamber 9|beneath the piston, vcausing vent valve 88 to un- 'seat andvent fluidunder pressure from the brake pipe through exhaust port 94, so `'thatbrake pipe pressure -is reduced .at 'a relatively rapid rate in excessof the usual service lrate in accordance with the particular'size ofport '94 employed.

The reduction infbrake pipe pressure `at 4a relatively lrapid rate inexcess of the usual .service rate causes the fluid pressure -in pistonchamber :21 to reduce accordingly, whereupon the fiuid pressure in slidevalve chamber 29 causes 'rapid movement of the piston 28 to theleft, asviewed in Fig. 1,*until the piston `strikes 'extension 60 of As`top`58.lnview Aof the relatively rapid reduction in piston chamberpressuratheunbalance of fluid pressure exerted on `piston '28 from slide vvalvechamber 29 is sufficient tocause theA piston to continue to move totheleft after striking theextenvsion 68 and compress the spring 59 luntilstop member `58 rstrikes the end of stem 58, `which prevents furthermovement of piston 28 to the left, dueto the effective uid pressurelacting on `the 'outer area o'f Ypiston valve'61 in chamber`65.

Initial movement of 4piston 28 tothe le'ft causes Iauxiliary slide4valve 3| to close ,port |89, thereby -cuttingoi the supplementaryreservoir l1 .from slide 'valve Ichamber 29, and to uncoverthefserviceport II2 in themain slide valve 30 at thezseat vof theauxiliary slide valve. Further `movement of the pistoncauses the mainslide valve 39 to move and establish a communication 'for the supply offluid under pressure to the brake cylinder I5 from auxiliary reservoir"|8, through passage |98, slide valve chamber 29, port |:I2 in `the mainslide valve,'and port and passage 'I I3.

In view of the greater rapidity of brake p'rpe pressure reduction ascompared lto the usual ser-vice rate of reduction, and the correspondinggreater rapiditywith which the main slide valve '38 is moved to itsservice position, as just -d'escribed, fluid is immediately andrapidly-supplied to the brakecylinder to effect an 'application of thebrakes ina shorter time thanis effectedl thereby in -response to theusual .-serviceLrate of reduction in brake pipe pressure.

When 'a desired .amount vof Vreduction in brake -pipe pressure has beeneffected, vbrake-.valve 3is moved to Elap position 'wherein allcommunications are closed,'as:shown.in.Fig. 2, including that betweenthe equalizing A'reservoir Aand .the reduction limiting reservoir.

Vlh'enbrake pipe pressurer acting-in chamber 9| beneath equalizingpiston 81 decreases .below the equalizing reservoir pressure effective.in equalizing chamber .89 above the 'equalizing piston, the .latteripressure is effective to movethe equalizing piston '81 downwardly 4to'immediately close hvent valve 88 fand cut `off further reduction 'inbrake pipe pressure.

As soon as lthe `fluid pressure in :slide valve chamber `29 falls belowthe brake pipe pressure effective in'piston .chamber 21, piston 28 ismoved back until Ia 'shoulder oni-.he piston stem'32 engages the left'edge of the main slide `valve 38, as `viewed 'in Fig. 1, whereuponfurther movement of the piston 28 'is stopped inasmuch as the'fluidpressure differential acting to movepiston 28 backis insufficient toovercome the friction between the main rslide valve andits seat.

The auxiliary slide valve .33| is thus moved back :relatively'to themainfslidevalvefa suicient distance to close service port |I2 inthe mainslide valve .and cut oit the furthersupply of fluid under pressure'through the port .I I2 to the brake cylinder. The brakes, therefore,are held yapplied inthe desired degree.

In order to obtain a greater degree of service application, thebrakevalve I3 is-again moved'to 'service position,.held there =unti1 thekfurther degree of brake pipe pressure reduction as desired is effected,and then moved to lap position.

A full service application ,is obtained by .allowingxthe brake valve I3to remain 4in service posiltion until the equalizing reservoir I9 vhasfully equalized into the reduction limiting reservoir 28. The maximumamount 'of brake pipe pressure *reduction fora service'application isthus llimited to a predetermined amount as defined by the pressure ofequalization attained in equalizing chamber 89 :of the `brake valve |*3inasmuch as the ventvalve 88 is operated to cutoff :further vventing ofthe brake pipe through port 94 after the brake pipe pressure has reducedto that acting in the equalizing-chamber 89.

The capacities ofthe -equalizing and reduction limiting reservoirs maybe suitably proportioned to obtain any desired pressure -ofequalization, but they are preferably proportioned to obtain a pressure:of equalization, such `as forty-five pounds per square inch, `which isa few pounds less than "the pressure of equalization between theauxiliary reservoir I8 and brake cylinder I5, in order to ensure a fullapplication of .the brakes.

The fluid pressure acting in chamber 65 on the outer area of pistonvalve 61 Vand that;acting in passage I5 on the inner seated area of thepiston valve 8l bothreduce simultaneously with the reduction in brake`pipe pressure but the effective force of the differential pressure, asdetermined by the ratio ofthe outer area of piston Valve 61 inchamber-65 -to the inner seated area thereof as well as the area of thepiston valve itself, is suicient to hold 4.the piston valve 81 seated onits rib Aseat 'I8 as long as the brake pipe pressure does :not go belowthe predetermined set-lirnit, of for example, forty-five pounds vper.square .inch pressure.

Thus, by automatically vlimiting the amount of the'reduction in brakepipepressure for a serv.-

ice application, it is possible for the brake pipe exhaust iport ..94 ofbrake valve I3 to baci-any suitable size to eect any desired rate ofreduction in brake pipe pressure greater than the usual service rate,Without danger of exceeding the predetermined set limit of reduction,below which the piston valve 61 Will open to permit an emergencyapplication of the brakes to be effected, as hereinafter described.

At the completion of a full service application, the auxiliary slidevalve 3| and main slide valve 30 remain in service position, the excessof pressure in the auxiliary reservoir eiective in 'slide valve chamber29 over the reduced limit of brake pipe pressure eiective in pistonchamber 21 maintaining the piston 28 in the service position.

If it is desired to eiiect an emergency application of the brakes, thebrake valve is moved to emergency position, as diagrammatically shown inFig. 2, wherein both the brake pipe passage 93 and passage I DI leadingfromv the equalizing chamber 89 and equalizing reservoir I9 areconnected to the exhaust port and passage 95. As a result, brake pipepressure is reduced at an emergency rate by simultaneous venting throughexhaust port and through vent port 84 which opens when vent valve 88 isunseated by the lifting of the equalizing piston 8l.

It will be noted that in the emergency position of the brake valve I3,no connection is established between the equalizingreservoir I9 and thereduction limiting reservoir 20, as in the service position.Consequently brake pipe pressure continues to reduce at the emergencyrateY as long as the brake valve is maintained in the emergencyposition. Y i

The r-eduction in uid pressure in piston cham-. ber 2'I of the triplevalve device is initially eiective as above described for I movement ofthe brake valve to service position, the piston 28 and slide valve 30being prevented momentarily from moving beyond a service position intoemergency position until the brake pipe pressure effective in pistonchamber 2'I is reduced a certain amount, such as five pounds, below thepredetermined limit of forty-five pounds per square inch set by thereduction limiting device. Obviously piston valve II may be so designedto give other marginal values than the ve pounds.

When the brake pipe pressure effective in piston chamber 2'I is reducedby this marginal value below the predetermined set limit of reduction inbrake pipe pressure, the fluid pressure eiective in slide valve chamber29 causes a suiciently great differential of pressure to act on thepiston 28 that the opposing iluid pressure force acting on piston valve61 is overcome, and the piston valve is unseated from its rib seat 10.

When the piston valve 61 is unseated, fluid at brake pipe pressure owsfrom passage 'I5 past the rib seat I0 into the annular chamber 'I3 andthus the fluid under pressure acting on both sides of the piston valveI'I is substantially equalized andthe piston 28 is thereby permitted tomove positively into emergency position, wherein an emergencyapplication of the brakes is effected, as hereinafter described. Thechoke passage 'I4 may be of any suitable flow area adapted to sorestrict the venting therethrough of iiuid under pressure from chamber'I3 at the inner side of the piston valve 81 to atmosphere, that thepiston 28 may move positively to emergency application position. It willthus be seen that the marginal decrease of, for example, ve

. pounds below the predetermined reduction limit in brake pipe pressureis for the purpose of preventlngthe occurrence of an undesiredemergencyapplication when only a full service application is intended. l

When the main slide valve 30 is in emergency position it establishes aconnection between pas- Sage- 40 leading to high pressure valve chamber39 and brake cylinder passagev II3, through a cavity I I5 in the mainslide valve 38 and a branch passage II4. Fluid under pressure in chamber39 thus iioWs into the brake cylinder, and in so doing reduces the uidpressure above high pressure valve piston 38 so that the higherauxiliary reservoir pressure in chamber 35 beneath the piston 38 iseffective to lift the piston and thus cause the valve 43 to unseat fromits rib seat 46. Fluid under pressure may then be supplied from thesupplementary reservoir II to the slide valve chamber 29 through pipeand passage 45, past valve 43, through passage 5I, chamber 49 andpassage 36.

Whenv the main slide valve 38 is4 in emergency position, a communicationis established for the supply of fluid under pressure from slide valvechamber 29 to the brake cylinder I5 through emergency port IIB in themain slide valve 30, and port and passage II3. In View of the fact thatboth the auxiliary reservoir and the supplementary reservoir areconnected to the slide valve chamber 29, the ultimate force of brakeapplication is, therefore, greater for an emergency application than fora service application. Once the main and auxiliary slide valves havebeen moved into emergency position, they remain there as long as thehandle 84 of the brake valve I3 remains in emergency position and thuscause full equalization of the pressures in the brake cylinder I5, theslide valve chamber 29, the auxiliary reservoir I 6, and thesupplementary reservoir I'I togbe eiected. It will be clear that such isthe case because of the excess of the pressure in the slide valvechamber 29 over the reduced brake pipe pressure effective in pistonchamber .21. Furthermore, due to the fact that the piston valve 6'I isheld unseated from its annular seat rib 'I0 by the piston 28 actingthrough the stem 58,-continued reduction in brake pipe pressure at arestricted rate takes place through the choke 14 even if the handle 84of the brake valve I3 is returned into lap position following theemergency application of the brakes. The brakes thus remain applieduntil such time as they are released by movement ofthe brake valve- I3to release position, shown in'Fig. 1. In this position of the brakevalve I3, the brake pipe and equalizing reservoir are charged with fluidfrom the main reservoir I8 as previously described, the admission offluid into pistonV chamber 2'I forcing the piston 28 back into releaseposition wherein the brake cylinder I5 is vented to atmosphere throughpassage I I 3, cavity I I5 in the main slide valve 30, port III, cavityII8 in the auxiliaryslide valve 3I, cavity 'or passage II9 in the mainslide valve and exhaust port and passage |29. It will be noted also thatthe reduction limiting reservoir` 20 is connected to atmosphere throughexhaust portand passage 95 so that the iluidrpreviously dischargedthereinto is completely vented and the reservoir conditioned for anotheroperation of the brake valve to service position.

Restricted opening or choke I4 is eective on recharge to permit'thepiston 28 to be moved to release position, in that it so restricts theblowdown or exhaust of brake pipe pressure on the charge` or rechargeoperation, that pressure suf- .cient to move the piston 28 back torelease poaogarot sition is built up in piston-chamber 21. The. pistonvalve 61 is thus reseated on the rib seat 10,. as the piston 28 movesaWay from the stop member 58, by the brake pipe pressure effective inchamber 65 assisted by return spring 11.

It is to be noted that while, in effecting an emergency application, aservice application is momentarily caused, this is unobjectionablebecause of the rapidity with which the service application is effected.

It will thus be clear that my invention possesses an advantage over thepresent standard equipment in that it enables a service application ofthe brakes to be effected rapidly enough so that an. emergencyapplication is not required, also thereby enabling quicker rechargingand lesser time to release the brakes than required after an emergencyapplication of the brakes.

summarizing, my invention comprises essentially a valve device simplyand inexpensively adapted to usual brake controlling equipment,

' which is differentially subjected to brake pipe pressure and which iseffective to prevent movement of a brake controlling valve device beyonda service positionl into emergency position, regardless of the rate ofreductio-n of brake pipe pressure, until at least a predeterminedreduction in brake pipe pressure has been effected, in which case itiseffectiveto'permit; the brake controlling valve device to move into aposition for effectingV an emergency application of the brakes.Furthermore, by providing a brake pipe pressure reduction limitingdevice effective when the brake valve is moved to service position, anundesired emergency application is` incapable ofv being. effectedregardless of the rate of reduction in brake pipe pressure.

While but one embodiment of my invention has been illustratedanddescribed, it will be understood that changes, additions or omissionsmay be made therein Without. departing'fromthe spirit` ofthe invention.I desire, therefore, tot impose no restrictionsy as to the scope of myinvention except as necessitated by the prior art and. as defined in theappended claims.

I-Iaving now described my invention, what I claim asinetv and desire tosecure by Letters Patent, is:

l. In afluid pressure brake, the combination with a brake pipe, a brakecylinder, and a brake controlling valve device movable to a serviceapplication position in Which fluid` under pressure is supplied to thebra-ke cylinder upon a reduction in brake pipe pressure and to anemergency application position in which fluid under pressure is suppliedto the brake cylinder upon a sufficiently rapid rate-of reduction inbrake pipe pressure, of means effective as long as the brake pipepressure does not reduce below a predetermined uniform pressure forpreventing movementofY said valve device-to emergencyl applicationposition..

2. In a fluid pressure brake, the combination with a brake pipe, of abrake valve device adapted in service position toeffect a reduction inbrake pipe pressure at a rate substantially greaterthan theusual servicerate, a brake controlling valve device movable to a serviceapplicationposition upon a reduction brake pipe pressure and to an emergencyapplication position upon a suciently rapid. rate. of reduction` inbrake pipe` pressure, and means` for preventing movement of said valvedevice-to emergency application position. until the brake pipe pressurehas been reduced belovvV a predetermined, uniform pressure.

3; In a fluid pressure brake the combination with a brake pipe and abrake controlling valve device operative upon variations in brakev pipepressuretoV effect the. operationof the brakes, of a brake valve device;adapted when in service-position to effect a reductionin brakepipepressure at a. rate substantially in excess of. the usual servicerate,.andy meansy for preventing said brake controlling valve devicefrom operating to effect an emergency application of the brakes WhenSaid brake valve is inservice position.

4. Ina fluid pressure brake, the combination with a. brakepipeand abrake controlling valve device operative upon variations in brake pipepressure to effect the, operation of the brakes,v of a brakevalve'device-adapted when in servi-ce position to effect a reduction inbrake-pipe pressure at a rate substantially in excess of the usualservice rate., and means for causing said brake controlling valve deviceto be responsiveto. such rate of reduction in brake pipe pressure inexcess of the usual service rate to effect only a service application,said means including means effective when said brake valve device is inservice position to limit the reduction in brake pipe pressure to apredetermined amount, andmeans effective upon a reduction in brake pipe.pressure less than said predetermined amount. for preventing said brakecontrolling valve device from operating to effect an emergencyapplication of the brakes.

5. In a fluid pressure brake, the combination with a brake. pipe and abrake controlling valve device operative upon variations in brake pipepressure to effect the operation of thebrakes, of a brake' valvedeviceadapted when; in service position to effect a reduction in brake pipepressure at a rate substantially in excess; of the usual service rate,and means for causing said brake controlling valve. device-to beresponsive to such rate of reduction,y in brake pipe pressure in excessof the usual service rate to effect only a service application, saidmeans including means effectivevvhen said brake valve device is inservice position to limit the reduction in brake pipe pressure to apredetermined amount, and means comprising al movable abutmentdifferentiallyv subject to the opposing forces exerted by brake pipepressure effective on opposite sides thereof and effective upon areduction in brake pipepressure less than said predetermined amount forpreventing said: brake controlling valve device from operating. toeffectan emergency application of the bra-kes.

6. In a fluid pressure brake, the combination Withv a brake pipe. and.ya brake controlling valve device having fluid pressure responsive meanssubject to brake pipe pressure and operative to onepositionto effect a.service application of the brakes and to` anotherposition to effect anemergency applicationl of the brakes, in response to variationsin brakerpipe pressure, of a brake valve device adapted when in service positionto effect a reduction-in brake pipepressure at a rate substantially inexcess of the usual service rate,v and means. for causing said brake.controlling valve device to be responsiveto such rate of reduction inbrakepipe pressure-in excess of the-usual service rate to effect onlyaservice application, said means including meansfeffective when saidbrake valve device is in service position to limit the reduction, inbrakepipe pressure to a predetermined. amount', and means engageable bysaid fluid pressure responsive means4v and effective lOf upon areduction in Vbrake pipe pressure less than said predetermined amountfor preventing said fluid pressure responsive means from operating tothe position for effecting an emergency application of the brakes.

'7. In a iiuid pressure brake, the combination with a brake pipe, of abrake controlling valve device having uid pressure responsive meanssubject to brake pipe pressure and operative upon a reduction in brakepipe pressure at an emergency rate to move successively into a serviceapplication position and an emergency application position, of means forresisting movement of said uid pressure responsive means from serviceapplication position to emergency application position in eifecting anemergency application of the brakes until the brake pipe pressure isreduced below a predetermined pressure regardless of the rate ofreduction in brake pipe pressure, after which said means yields to thefluid pressure force acting to move said fluid pressure responsive meansand permits said uid pressure responsive means to move into emergencyapplication position.

8. In a iiuid pressure brake, the combination with a brake pipe, a brakecylinder, and a brake controlling valve device movable into a serviceapplication position upon a reduction in brake pipe pressure and to anemergency application position upon a sufficiently rapid rate ofreduction in brake pipe pressure, of a movable abutment adapted to bemaintained in one position as long as the brake pipe pressure does notreduce below a predetermined pressure to prevent movement of said valvedevice to emergency position and adapted to be moved out of said oneposition only when the brake pipe pressure reduces below saidpredetermined pressure to permit said valve device to move intoemergency position.

9. In a fluid pressure brake, the combination with a brake pipe, a brakecylinder, and a brake controlling valve device movable to a serviceapplication position in which` fluid under pressure is supplied to thebrake cylinder upon a reduction in brake pipe pressure and to emergencyapplication position in which fluid under pressure is supplied to thebrake cylinder upon a sufficiently rapid rate of reduction in brake pipepressure, of a movable abutment differentially subject to the opposingforces exerted by brake pipe pressure on opposite sides thereof as longas the brake pipe pressure exceeds a predetermined value, for

preventing movement of said brake controlling valve device to emergencyapplication position.

10. In a fluid pressure brake, the combination with a brake pipe, abrake cylinder, and a brake controlling valve device movable to aservice application position in which fluid under pressure is suppliedto the brake cylinder upon a reduction in brake pipe pressure and toemergency application position in which fluid under pressure is suppliedto the brake cylinder upon a su'iciently rapid rate of reduction inbrake pipe pressure, of a movable abutment differentially subject to theopposing forces exerted by brake pipe pressure on opposite sides thereofin constant ratio regardless of the rate of reduction in brake pipepressure as long as the brake pipe pressure exceeds a predeterminedvalue, for preventing movement of said brake controlling valve device toemergency application position.

11. In a fluid pressure brake, the combination with a brake pipe, abrake cylinder, and a brake controlling valve device movable to aservice application position in which fluidunder pressure is supplied'to the brake cylinder upon a reduction in brake pipe pressure and toemergency application position in which fluid under pressure is suppliedto the brake cylinder upon a sufficiently rapid rate of reduction inbrake pipe pressure, of a movable abutment differentially subject to theopposing forces exerted by brake pipe pressure on opposite sides thereofas long as the brake pipe pressure exceeds a predetermined value, forpreventing movement of said brake controlling valve device to emergencyapplication position, and means for preventing a reduction in brake pipepressure below said predetermined value.

12. In a fluid pressure brake, the combination With a brake pipe, abrake cylinder, and a brake controlling valve device movable to aservice application position in which ilud under pressure is suppliedtothe brake cylinder upon a reduction in brake pipe pressure and toemergency application position in which fluid under pressure is suppliedto the brake cylinder upon a sumciently rapid rate of reduction in brakepipe pressure, of a movable abutment differentially subject to theopposing forces exerted by brake pipe pressure on opposite sides thereofin constant ratio regardless of the rate of reduction in brake pipepressure as long as the brake pipe pressure exceeds a predeterminedvalue, for preventing movement of said brake controlling valve device toemergency application position, and means for preventing a.

reduction in brake pipe pressure below said predetermined value.

13. In a luid pressure brake, the combination with a brake pipe, a brakecylinder, and a brake controlling valve device movable to a serviceapplication position in which fluid under pressure is supplied to thebrake cylinder upon a reduction in brake pipe pressure and to emergencyapplication position in which fluid under pressure is supplied to thebrake cylinder upon a sufficiently rapid rate of reduction in brake pipepressure, of a movable abutment constantly subject on the entire oneside thereof to brake pipe pressure and on the other side in part tobrake pipe pressure and in part to atmospheric pressure as long as thebrake pipe pressure exceeds a predetermined value, the diierential inthe fluid pressures acting on said abutment being eective to cause saidabutment to prevent movement of said brake controlling valve device intoemergency application position as long as the brake pipe pressureexceeds the said predetermined value.

14. In a uid pressure brake, the combination with a brake pipe, a brakecylinder, and a brake controlling valve device movable to a serviceapplication position in which uid under pressure is supplied to thebrake cylinder upon a reduction in brake pipe pressure and to emergencyapplication position in which fluid under pressure is supplied to thebrake cylinder upon a sufficiently rapid rate of reduction in brake pipepressure, of means for preventing movement of said valve device toemergency position in response to said sufficiently rapid rate ofreduction in brake pipe pressure, as long as the brake pipe pressuredoes not reduce below predetermined uniform pressure.

15. In a iiuid pressure brake, the combination with a brake pipe, abrake cylinder, and a brake controlling valve device movable to aservice application position in which fluid under pressure is suppliedto the brake cylinder upon a reduction in brake pipe pressure and toemergency application position in which fluid under pressure is suppliedto the brake cylinder upon a sufficiently rapid rate of reduction inbrake pipe pressure, of

means eiective to prevent movement of said valve device to emergencyposition regardless of the rate of reduction in brake pipe pressure, andmeans operative upon a reduction in brake pipe pressure below apredetermined' pressure for rendering said last means ineffective.

16. In a fluid pressure brake, the combination with a brake pipe, abrake cylinder, and a brake controlling valve device movable to aservice application position in which fluid under pressure is suppliedto the brake cylinder upon a reduction in brake pipe pressure and toemergency application position in which fluid under pressure is suppliedto the brake cylinder upon a sufciently rapid rate of reduction in brakepipe pressure, of a movable abutment differentially subject to theopposing forces exerted by fluid under pressure acting on opposite sidesthereof for preventing movement of said valve device to emergencyposition regardless of the rate of reduction in brake pipe pressure, andmeans operative upon a reduction in brake pipe pressure below apredetermined pressure for effecting the equalization of fluid pressureforces acting on said abutment and thereby rendering said abutmentineffective to prevent movement of said valve device to emergencyposition.

1'7. In a fluid pressure brake, the combination with a brake pipe, abrake cylinder, and a brake controlling valve device movable to aservice application position in which fluid under pressure is suppliedto the brake cylinder upon a reduction in brake pipe pressure and toemergency application position in which fluid under pressure is suppliedto the brake cylinder upon a sufficiently rapid rate of reduction inbrake pipe pressure, of graduating means for restraining movement ofsaid valve device from service position to emergency position, a movableabutment adapted to be maintained in one position as long as the brakepipe pressure does not reduce below a predetermined pressure to preventmovement of said valve device to emergency position and adapted to bemoved out of said one position only when the brake pipe pressure reducesbelow said predetermined pressure to permit said valve device to moveinto emergency position, and a spring adapted to aid in the return ofsaid abutment to said one position.

JOHN B. HULL.

